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adequacy for potential heights. The dangers of oxygen
deprivation should not be taken lightly. At around
20,000 feet MSL pilots might have only 10 minutes of
“useful consciousness.” By 30,000 feet MSL, the timeframe
for “useful consciousness” decreases to one
minute or less! For planned flights above 25,000 feet
MSL, an emergency oxygen back-up or bailout bottle
should be carried.
Proper clothing is a must since temperatures of –30° to
–60°C may be encountered at altitude. Proper preparation
for the cold is especially difficult since temperatures
on the ground are often pleasant on wave soaring
days. Sunshine through the canopy keeps the upper
body amazingly warm for a time, but shaded legs and
feet quickly become cold. Frostbite is a very real
threat. After an hour or two at such temperatures, even
the upper body can become quite cold. Layered, loose
-fitting clothing aides in insulating body heat. Either
wool gloves or light fitting gloves with mittens over
them work best for the hands. Mittens make tasks such
as turning radio knobs difficult. For the feet, two or
three pair of socks (inner silk, outer wool) with an insulated
boot is recommended.
Within the continental United States, Class A airspace
lies between 18,000 and 60,000 feet MSL (FL 180 to
FL 600). Generally, flights in Class A must be conducted
under Instrument Flight Rules (IFR). However,
several clubs and glider operations have established
so-called “Wave Windows”. These are special areas,
arranged in agreement with Air Traffic Control (ATC),
in which gliders are allowed to operate above 18,000
feet MSL under VFR operations. Wave windows have
very specific boundaries. Thus, to maintain this privilege,
it is imperative to stay within the designated window.
On any given day, the wave window may be
opened to a specific altitude during times specified by
ATC. Each wave window has its own set of procedures
agreed upon with ATC. All glider pilots should become
familiar with the procedures and required radio frequencies.
True Airspeed (TAS) becomes a consideration at
higher altitudes. To avoid the possibility of flutter,
some gliders require a reduced indicated never-exceed
speed as a function of altitude. For instance, at sea
level the POH for one common two-seat glider, the
VNE, is 135 knots. However, at 19,000 feet MSL it is
only 109 knots. Study the glider’s POH carefully for
any limitations on indicated airspeeds.
There is always the possibility of not contacting the
wave. Sink on the downside of a lee wave can be
high—2,000 fpm or more. In addition, missing the
wave often means a trip back through the turbulent
rotor. The workload and stress levels in either case can
be high. To reduce the workload, it is a good idea to
have minimum return altitudes from several locations
calculated ahead of time. In addition, plan for some
worse case scenarios. For instance, consider what offfield
landing options are available if the planned minimum
return altitude proves inadequate.
A normal preflight of the glider should be performed.
In addition, check the lubricant that has been used on
control fittings. Some lubricants can become very stiff
Rotor Cloud
Cap Cloud
Lenticular
Clouds
Figure 10-19. Rotor and cap clouds with lenticulars above.
10-13
when cold. Also, check for water from melting snow or
a recent rain in the spoilers or dive brakes. Freezing
water in the spoilers or drive brakes at altitude can
make them difficult to open. Checking the spoilers or
dive brakes occasionally during a high climb helps
avoid this problem. A freshly charged battery is recommended,
since cold temperatures can reduce battery
effectiveness. Check the radio and accessory equipment,
such as a microphone in the oxygen mask even if
it is not generally used. As mentioned, the oxygen system
is vital. Other specific items to check depend on
the system being used. A checklist such as PRICE is
often helpful. The acronym PRICE stands for:
• Pressure—Check pressure in the oxygen bottle.
• Regulator—Check at all settings.
• Indicator—Check flow meters or flow-indicator
blinkers.
• Connections—Check for solid connections, possible
leaks, cracks in hoses, etc.
• Emergency—Check that the system is full and
properly connected.
A briefing with the towpilot is even more important
before a wave tow. Routes, minimum altitudes, rotor
avoidance (if possible), anticipated tow altitude, and
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Glider Flying Handbook(143)
